Process of treating steel shapes.



J. BRUNNER.

PROCESS OF TREATING STEEL SHAPES.

APPLICATION FILED FEB. 1. I911.

LQY'LWQD Patented Sept. 3,1918.

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JOHN BRUNNEB, EVANSTON, ILLINOIS.

PROCESS OF TREATING STEEL SHAPES.

Specification of Letters Patent.

Patent-ed Sept. 3, 191%..

Application filed February 1, 1917. Serial No. 145,960.

To all whom it may concem:

Be it knownthat I, JOHN BRUNNER, a citizen of the United .States, and resident of Evanston, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Processes of Treating Steel Shapes, of which the following is a specification.

'My invention relates to steel making and has particular reference to a novel method of finishing rails and similar rolled shapes.

Improvements in the methods of producing, handling and treating railroad rails are imperative in View of the great increase in the requirement of the service. In the production of rails by the processes now in common use, there is a tendency toward coarseness of structure or crystallization in the inner part of the rail head. This is ac companied with a low ductility of the center part of the head and may result in early fatigue of the steel in service, causing breakages which cannot be foreseen. Various forms of heat treatment have been attempted with the view of producing improvement in the structure of the interior of rails, but the difficulties encountered in the operations required for the treatment seem to prevent these methods being used in commercial production of rails. The method I propose requires a small amount of additional equipment in the existing rail mills and the rails will be completed in a regular sequence of operations without reducingthe standard speed of production.

The method is based on the theory that" when a rolled article is' allowed to cool-below the temperature of recalescence a certain grain structure is formed which may be changed to a new grain structure ifthe article is reheated to a point above the thermal critical range. This is well known, but I have conceived that a new and advantageousgresult is secured if, after a finer grain has been obtained by reheating to a point slightly above the thermal critical range,.it is re-rolled to the finished size and then slowly cooled to atmospheric temperature, thereby producing an article of uniform fine grain with a hard exterior finish.

In practice the method comprisesthe steps of rolling the rail toa size slightly in excess of that of the finished rail, the rail to cool slowly to a temperature be low that of recalescence, then reheating the rail slowly and evenly to a temperature allowing slightly above the upper limit of the thermal critical range, until the structure attains a fine grain, then re-rolling the rail, or in effect giving it the final pass-or passes, then allowing it to slowly cool on a hot bed. Preferably before being received on the hot bed the rail may be passed through straightening and cambering rolls.

'Rails produced in accordance with this method will be found to have a finer and more uniform. grain structure throughout the cross section; they will present a better finish than is possible to obtain by the present methods; they will have greater ductility, both in the head and in the web, than is found in the present rails and the wear and breakage resistance will be materially increased.

Iii-order to arrive at a better understanding of the method, reference is had to the accompanying drawing, in which the figure 1s a diagrammatic illustration of a mill laid out in accordance with the present invention.

A finishing stand of rolls 10 is adjusted to roll the rails to a size slightly greater than that of the desired finished rail. The rails are then presented to the hot saws 11, from which they are conducted by the transfer tables 12 to a cooling bed 13.

The rails leave the finishing pass 10 at a temperature of approximately 1000 C. At the termination of the following manipulations and the completion of travel over the hot bed 13, the temperature is below 700 C. The exact temperature will vary according to the chemical composition of the steel, the intention being that the cooling shall proceed to a point where the temperature is just below the thermal critical range or temperature of recalescence. 7

After leaving the hot bed 13 the rails are transferred into a reheating furnace 141-, wherein the temperature is slowly raised to a point between 800 C. and 1000 0., until a fine grain results. Preferably the reheating temperature should be only sli 'htly above the thermal critical range, care eing taken to avoid overheating. After leaving the reheating furnace 14:, the rails are passed through a stand of rolls 15, where the rails are rolled to the finished size, thus giving the exterior a hard finish. A. stand of straightening or cambering rolls 16 may be located at a point adjacent to the finishing rolls. After leaving the straightening rolls fer table 18 for suitable disposition.

Rails finished in the manner referred to will be found to have a better surface, a

more uniform and finer grain structure and a greater strength than has been common in rails produced heretofore.

I claim:

1. The method of treating steel shapes, which consists in rolling the same to a cross sectional area slightly greater than the finished area, permitting the shapes to cool to a point below the thermal critical range, reheating to a temperature slightly above the thermal critical range whereby a finegrained structure is formed, and finally rolling the shapes to the finished area, sub stantially as described.

2. 'The method of treating steel shapes, which consists in rolling the same to a cross- I sectional area slightly greater than the finamar/a ished area, permitting the shapes to cool to a temperature below approximately 700 (1., then reheating to a temperature above 800 C. but under 1000 (3., whereby a finegrained structure is formed, and finally rolling to the finished area.

3. The method of finishing steel rails, which consists in rollingthe same to a' crosssectional area slightly greater than the finished area, allowln the rails to cool below the thermal'critica range, reheating, to a temperature slightly above the thermal critical range, whereby a fine-grained structure is formed, and finally rolling the rails to the finished area, substantially as described.

Signed at Chicago, Illinois, this 26th day of January, 1917.

JUHN BRUNNER.

Witnesses:

W. E. DANIELS, CHAnLns R. TAMnr. 

